Sterling silver (or STS) is an alloy of silver containing 92.5% by mass of silver and 7.5% by mass of other metals, usually copper. The sterling silver standard has a minimum millesimal fineness of 925. Fine silver (99.9% pure) is generally too soft for producing functional objects; therefore, the silver is usually alloyed with copper to give it strength but preserving the ductility and beauty of the precious metal. Over the years, some countries developed systems of hallmarking silver. The purpose of hallmark application is used to indicate the purity of the silver alloy used in the manufacture or hand-crafting of the piece.